DIY Diodes

[H. P. Friedrichs], the creator of the Static Bleeder has created his own diodes. Using household chemicals, a film of cuprous oxide was made on a copper pipe cap. Cuprous oxide has been one of the first known semiconductor substances, has a low forward drop but is an otherwise asymmetrical conductor, odd V-I curves, and some neat photovoltaic action. The apparatus seen above is used to bring a piece of lead (in this case, solder) into contact with the salmon-colored cuprous oxide while electrical connections can be made to the binding posts at the front. What are your thoughts on this device?

I skimmed the article, but I didn’t see any information on the characteristics of the diode. I did a quick search and turned up the following.

Copper oxide has a knee of 0.2V, but the reverse breakdown voltage is around 5 Volts, so for many applications a series of diodes is used to increase the reverse breakdown (and as a side effect the knee voltage will be higher). The other drawbacks are metallic rectifiers are affected by temperature, atmospheric conditions (I guess could be fixed by different construction), and aging (e.g. resistance goes up over time).

“Am I wrong for immediately picturing a second oxide pipe cap at the other end of the solder, creating a very crude transistor?”

That is the equivalent of connecting the anodes or cathods of two diodes – which AFAI remember doesn’t make a transistor. A transistor isn’t just two diodes – it is a sandwich of two pieces of bread with some semiconductor meat between them e.g. NPN has P-type semiconductor meat. When you put a voltage onto one PN junction it starts conducting and that changes the electrical properties of the P so that the other junction conducts too. That doesn’t happen with two open meat sandwiches (two diodes) with wire between the meat.

I am trying to think of a good car analogy using a freeway, an on-ramp, and an off-ramp with a road jam and charge carrier cars…

I wonder if he’s thought of using silicon carbide (carborundum) crystals? It has pretty good diode characteristics, and can even make a blue LED!
(From http://en.wikipedia.org/wiki/Silicon_carbide):
Electronic applications of silicon carbide as light emitting diodes and detectors in early radios were first demonstrated around 1907, and nowadays SiC is widely used in high-temperature/high-voltage semiconductor electronics.

Oh, and @ Quin above; If he were to add another lead and poked around patiently, he might just be able to find two points on the surface that, along with the base connection, that act like a transistor.

Oleg Vladimirovich Losev just may have done just that in 1941, see here for details:

two of these, facing opposite ways in parallel as the feedback loop of an opamp = awesome distortion pedal. Different diodes don’t always clip identically over all frequencies, Just like when you replace the back to back diodes in a tube screamer or almost any generic distortion pedal. you can replace them with different kinds of leds (you can really hear the difference) or half transistors. power diodes almost always sound better for example.

@robocat
I didn’t assume it would be that easy. It’s not my field, so I wasn’t sure whether the whole stick of solder would be too large to behave as the entire junction. I take it that it would be.

But still, picture the mythical steampunk inventor, who just built a transistor. Then the over sized op-amp, and TTL.

@rooftop ridicule
Replace diodes? The schematics for those pedals are all over the place. Build one from parts! I used to keep several on breadboards. Multiple diodes on one direction, or none, to change the top or bottom of the wave form. Different caps and resistors to change the frequency response of the amp.

Pair this with the SiC whisker LED (Make your own LEDs) that was on HAD a while back, and you could get some really weird distortion.

This looks a lot like the old apparatus for holding a galena crystal and the phosphor-broonze wire (“cats whisker”) that formed the detector diode in old crystal radios. We built one using fool’s gold instead of galena. See it here:
More info on crystal set adventures here:

One of my lecturers was reminicising last year about making a transistor as Quin thinks above, when proper transistors were extremely expensive. iirc they sort of worked but the biggest problem he had was parameter differences between the two diodes.

What about combining with hematite as resistor and cupperwound coil …. hmm …. what about an active semiconductor: a transistor. Come on, go ahead. Make a complete diy oscilator that way because you sure know how to also make a capacitor. Try as much bare material as possible for the coil and capacitor only relying on the shape of the material. Dielectric being air … or other natural material. No plastics since it MUST last at least thousands of years. Yes you heard me right :) => 10.000 BC and EMP proof.